Etching machine



Feb. 1, 1955 w, GUENST 2,700,838

ETCHING MACHINE Fi led May 10, 1954 s Sheets-Sheet 1 INVENTOR. I/t zZ/zznz Guezzs ATTORNEYS Feb. 1, 1955 w. GUENST 2,700,838

ETCHING MACHINE Filed May 10, 1954 '5 Sheets-Sheet 2 INVENTOR. William Gaerzs ATTORNEY-9.

Feb. 1, 1955 w. GUENST 2,700,838

ETCHING MACHINE Filed May 10, 1954 5 Sheets-Sheet 3 ATTORNE Y6.

Feb. 1, 1955. w. GUENST 2,700,838

ETCHING MACHINE Filed May 10, 1954 5 Sheets-Sheet 4 a? k j 1NVENT0R.

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ETCHING MACHINE Filed May 10, 1954 5 Sheets-Sheet 5 W I ATTORNE rs United States Patent ETCHING MACHINE William Guenst, Elkins Park, Pa.

Application May 10, 1954, Serial No. 428,573

9 Claims. (Cl. 41-9) The present invention relates to etching machines of tl'lie character which are employed in etching printing p ates.

A purpose of the invention is to create a random motion of a printing plate with a wider scatter band of variation in angle.

A further purpose is to provide a rack, which rotates a plate mounting as a carriage reciprocates, with a pivotal mounting on a longitudinal axis and make the rack of screw form, preferably a helical coil and most desirably a helical coil spring, so that the reaction forces of the cooperating gear against the rack can rotate the rack and change the angle of motion of the plate support.

A further purpose is to compress a helical spring in a housing to restrain it against turning while permitting chance turning, and desirably to adjust the compression.

A further purpose is to restrain the helical coil spring by one or preferably two opposed weaker springs acting on the housing against the rack spring, and preferably to wind the weaker spring or springs in the same direction as the rack spring.

A further purpose is to provide a friction clutch in the drive to further vary the angle of turning according to a random distribution.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a few only of the numerous embodiments in which my invention may appear, selecting the forms shown from the standpoints of convenience in illustration, satisfactory operation and clear demonstration of the principles involved.

Figure l is a top plan view of the preferred embodiment of the etching machine of the invention.

Figure 2 is a front elevation of the etching machine of Figure 1 partially broken away to show the plate mounting.

Figure 3 isan enlarged fragmentary perspective of the random drive.

Figure 4 is an enlarged section on the line 4-4 of Figure 1, showing the random drive.

Figure 5 is a view corresponding to Figure 4 and showing a modification.

Figure 6 is an enlarged section on the line 66 of Figure 1.

Figure 7 is a plan section taken on the line 77 of Figure 4.

Figure 7a is a view similar to Figure 7 but showing a modification.

Figure 8 is a fragmentary view corresponding to Figure 7 and showing a modification.

Figure 9 is a vertical section of a modified etching machine in which the plate is supported in generally vertical position rather than in horizontal position.

Describing in illustration but not in limitation and referring to the drawings.

In etching machines for printing plates it is desirable to spray acid on the plate, and in some machines, in order to secure a maximum of uniformity of acid distribution, the plate is moved, desirably being reciprocated and rotated as shown for instance in Easley U. S. Patent 2,669,048, dated February 16, 1954, for Etching Machine.

Efforts have been directed toward producing motions of the plate mounting according to a random or chance plan, in order to avoid channeling or prevent local concentration of acid etch due to the position of reversal 30 "Ice been obtained, due in part to the tendency of such mechanisms to follow a restricted pattern and not give a wide scatter band of motion, and also because vibratory forces introduced in an efiort to obtain random variation in the motion have tended to destroy the mechanlsm.

The present invention is concerned particularly with obtaining a motion of the plate mounting which will vary widely and without restriction of pattern, so as to assure that the point of change or variation of the motion will not be localized or preferentially concentrated with respect to the area of the plate, and very uniform etching will be obtained.

Furthermore, in accordance with the present invention, a very high degree of ruggedness is introduced into the mechanism, and forces incident to starting, stop and reversing are absorbed resiliently and are made to contribute to the chance variation of the motion without destroying the mechanism.

In accordance with the invention a rack is employed to turn or rotate the plate mounting which is of helical form and capable of turning under the reaction. The rack is preferably a helical coil of wire or the like and is most desirably a helical compression spring. The spring is also desirably placed under compression to retard but not prevent rotation about the longitudinal axis of the spring. In the preferred form, a weaker spring or weaker springs, preferably of the same diameter and preferably wound in the same direction, apply compression at the ends of the rack spring.

Also in the preferred embodiment the chance variation is increased by use of a friction clutch in the drive between the gear and the plate mounting.

Considering now the form of the invention of Figures 1 to 8 inclusive, the etching machine comprises a frame 20 supporting a tank 21 which is provided with a sloping bottom 22, side Walls 23 and a cover 24. The circulation of acid to create the acid spray, as well known in the art, is accomplished by withdrawing acid from the bottom through a pipe 25, and pumping by a pump 26 driven through a pulley and belt arrangement 27 from an electric motor 28, the pump circulating through pipes 30 to acid sprays 31 inside the tank.

The acid level in the bottom of the tank is high enough to reach the bottom of distributing paddles or impellers 32 on shafts 33 which are journaled on the outside of the tank in bearings 34 and 35, but not high enough to cause leakage at the bearings. The paddles are driven by a system of pulleys and belts 36 from the motor 28 as well known.

The compartments in which the respective paddles operate are separated by vertical baflles 37 which run the length of the tank.

The lid is mounted for ready insertion and removal of the work, conveniently by pivoting at 38 at one side of the top of the tank, and providing counterbalance arms 40 which are pivotally connected at an intermediate point on the top of the tank at 41, and which extend out beyond pivot supports 42 to form extensions 43 which carry a counterweight 44. When the lid is tilted to raise it, its lower ends travel on rollers 45 on a track 46 at the top of the machine.

Considering now the random drive mechanism more in detail, the printing plate 47 to be etched is supported on the lower end of a plate mounting 48 as by adjustable clips 50 at the corners. The plate mounting 48 is secured to the bottom of a shaft 51, as by a bar 52 which is secured to the shaft by screw 53, screws 54 connecting the plate mounting to the bar. A bafile 55 is placed above the bar 52 to prevent acid spray from leaving the tank through slot 56 in the lid 24. Along one side of the baflle 55 an angle bafile 57 is secured to prevent spray from intruding into the space between the baflle 55 and the lid. The angle baffie 57 desirably runs somewhat beyond the range of movement of the shaft in the slot 56 at either end.

On the top of the lid a base 58 is mounted which carries end brackets 60 and 61 which secure guide rods 62 in generally horizontal parallel relation above the lid. A carriage 63 slides on the guide rod 62, having sliding bearings 64 beneath the carriage which guide the carriage in reciprocation through a range of movement permitted by the slot 56. The reciprocation of the carriage is controlled by electric motor on the lid, driving through pulley and belt combination 66 to speed reducer 67 which operates crank 68 pivotally connected to connecting rod 70, the opposed end of which is pivotally connected at 71 to the top of the carriage to reciprocate the carriage.

The shaft 51 is journaled in antifriction bearings 72 and 73 mounted on the carriage in a superstructure 74. At the upper end the shaft 51 has a reduced diameter portion 75 which is surrounded by gear 76 which is preferably of sprocket formation to engage a helical rack as later explained. In the preferred embodiment the gear is permitted to relatively move with respect to the shaft by friction clutch 77, consisting of a helical spring 78 surrounding the shaft, and opposed spring cups 80 and 81 around the shaft acting respectively against the inner retainer of bearing 73 and the gear 76. While the frictional clutch engagement of the gear to the shaft is preferred, the gear may be secured to the shaft as by a set screw 82 shown in Figure 5.

The gear engages a helical rack 83 which is preferably a helical compression spring, which extends throughout the interior of a tubular housing 84 having a longitudinal slot 85 through which the teeth of the gear extend. The tubular housing is desirably rigidly mounted at the ends in the brackets 60 and 61. In the preferred embodiment, as shown best in Figure 7, the housing 84 comprises an intermediate portion 85 which extends part way through mounting sockets 86 at the end, and also cup portions 87 at the ends having closed ends and held in the sockets 86 by set screws 88. The cup portions are adjustable in position lengthwise to control the compression of the spring 83 In the preferred embodiment, the rack spring 83 substantially conforms to the inside diameter of the housing, and is engaged at one or preferably at both ends by weaker helical springs 90 which are under compression between the ends of the housing, and tend to restrain the rack spring against turning. The weaker springs and the rack spring are preferably wound in the same direction to give satisfactory bearing areas at the ends. The weaker springs and the rack spring are also preferably of the same diameter.

In Figure 7a I show the center rack 23 as of solid material with teeth 83', but with the end spring 90 the same as in Figure 7.

In some cases the weaker spring can be omitted, and as shown in Figure 8 the rack spring 83 in this case extends the full length of the housing and is under slight compression longitudinally to provide some restraint against turning.

At the top of the shaft 51 is carried a dial indicator 91 which indicates the relative angular position of the shaft and therefore of the printing plate by reference to an index finger 92 on the superstructure of the carriage.

The invention can be applied as shown in Figure 9 for mounting a printing plate in which the plate is generally vertical, as well known in etching machines of the character of my U. S. Patent 2,651,869, granted September 15. 1953, for Etching Machine. In this form the tank 92 has a rotating paddle 93 which projects acid through a curved guiding channel 94 and receives air from a blower 95 through inlet jets 96 entering the acid stream. The plate mounting 48 and the mechanism for driving it may conform exactly to that already described except that it is placed on the vertical side instead of on the top in a horizontal or vertical position. The etching machine is suitably provided with an exhaust blower 97 and a gas flue 98 and is closed by a removable cover 100. In operation in any of the forms shown it will be evident that as the carriage reciprocates back and forth it will carry the shaft bodily and with it the gear, and the gear will turn in cooperation with the turns of the helical rack except insofar as the load is great enough to rotate the rack about its longitudinal axis.

This rotation of the rack about its longitudinal axis will occur to some extent under the reaction, particularly at points of reversal where the load may correspondingly increase, and will introduce a chance feature in the turning of the gear, as it will depend upon the frictional drag of the housing on the helical rack, and also the spring loading of the auxiliary springs 90, where used, at

the ends of the housing. There will also be a certain amount of longitudinal yield of the helical rack when it is of spring form, and this in itself will constitute a chance element in the turning of the gear.

While there will be a chance element introduced in this way it will be understood that there will be a resilient or cushioning effect which will not cause damaging vibration or shock since the springs can yield and the yielding will accommodate to the load of the gear.

If the gear is directly connected to the shaft as in Figure 5, the chance distribution or random distribution of the range of turning of the gear will turn the plate mounting accordingly, as the plate mounting is reciprocated by the carriage, and if, as in Figure 4, the gear is connected to the shaft by friction clutch, a further chance element is introduced, as the friction gear is free to slip to a variable extent with respect to the shaft.

It will therefore be evident that each time the plate is reciprocated through a series of revolutions or parts of revolutions it will end and reverse its rotation at different points. Thus, depending upon the setting, that is, the compression of the spring which retards the rotation of the helical spring rack, and the load on the friction clutch, it is possible to change the position of reversal or the total angle of turning by anywhere from a few degrees to 15 or 20 degrees or more each time the carriage reciprocates.

It will be understood that this can be adjusted as by adjusting the setting of the cups 87 longitudinally to tighten or loosen the springs 90.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. An etching machine including a tank and means in the tank for spraying acid on a printing plate to be etched, in combination with a carriage, means for reciprocating the carriage, a shaft rotatably mounted on the carriage, a plate support on the shaft on which the printing plate is mounted, a gear on the shaft, a rack in operative relation to the gear having a screw form and means for mounting the rack rotatably about an axis longitudinal of the rack in response to reaction forces of the gear against the rack, whereby a chance variation in the range of rotation of the plate support is obtained as the carriage reciprocates.

2. An etching machine according to claim 1, in which the rack is a helical coil.

3. An etching machine according to claim 1, in which the rack is a helical coil spring longitudinally under compression.

4. An etching machine according to claim 1, in which the rack is a helical coil spring longitudinally under compression, in combination with means for adjusting the longitudinal compression of the spring.

5. An etching machine according to claim 1, in which the rack is a helical coil, and the means for mounting permitting rotation of the same constitutes a slotted housing in which the helical coil is free to turn.

6. An etching machine according to claim 1, in which the rack and the means for mounting therefor comprise a housing having an opening therein, a first helical spring in the housing adapted to engage the gear, and an additional helical spring weaker than the first placed endwise with respect to the first and compressing the first spring longitudinally.

7. An etching machine according to claim 6, having a spring weaker than the first in the housing at each end of the first spring and retarding rotation of the first spring.

8. An etching machine according to claim 6, having additional helical springs in the housing on opposite ends of the first spring and under longitudinal compression, the additional springs being wound in the same direction and of the same diameter as the first spring but weaker than the first spring.

9. An etching machine according to claim 1, in combination with a friction clutch interposed in the drive between the gear and the plate mounting.

References Cited in the file of this patent UNITED STATES PATENTS l,l66,378 Levy Dec. 28, 1915 2,293,201 Gaebel Aug. 18, 1942 2,566,142 Powers Aug. 28, 1951 

